Data commit

Task/Grayscale-image/Erlang/grayscale-image.erl

@@ -0,0 +1,73 @@
+-module(ros_bitmap).
+
+-export([new/2, fill/2, set_pixel/3, get_pixel/2, convert/2]).
+
+-record(bitmap, {
+    mode = rgb,
+    pixels = nil,
+    shape = {0, 0}
+  }).
+
+tuple_to_bytes({rgb, R, G, B}) ->
+  <<R:8, G:8, B:8>>;
+tuple_to_bytes({gray, L}) ->
+  <<L:8>>.
+
+bytes_to_tuple(rgb, Bytes) ->
+  <<R:8, G:8, B:8>> = Bytes,
+  {rgb, R, G, B};
+bytes_to_tuple(gray, Bytes) ->
+  <<L:8>> = Bytes,
+  {gray, L}.
+
+new(Width, Height) ->
+  new(Width, Height, {rgb, 0, 0, 0}).
+
+new(Width, Height, rgb) ->
+  new(Width, Height, {rgb, 0, 0, 0});
+
+new(Width, Height, gray) ->
+  new(Width, Height, {gray, 0, 0, 0});
+
+new(Width, Height, ColorTuple) when is_tuple(ColorTuple) ->
+  [Mode|Components] = tuple_to_list(ColorTuple),
+  Bytes = list_to_binary(Components),
+  #bitmap{
+    pixels=array:new(Width * Height, {default, Bytes}),
+    shape={Width, Height},
+    mode=Mode}.
+
+fill(#bitmap{shape={Width, Height}, mode=Mode}, ColorTuple)
+    when element(1, ColorTuple) =:= Mode ->
+  new(Width, Height, ColorTuple).
+
+set_pixel(#bitmap{pixels=Pixels, shape={Width, _Height}, mode=Mode}=Bitmap,
+    {at, X, Y}, ColorTuple) when  element(1, ColorTuple) =:= Mode ->
+  Index = X + Y * Width,
+  Bitmap#bitmap{pixels=array:set(Index, tuple_to_bytes(ColorTuple), Pixels)}.
+
+get_pixel(#bitmap{pixels=Pixels, shape={Width, _Height}, mode=Mode},
+    {at, X, Y}) ->
+  Index = X + Y * Width,
+  Bytes = array:get(Index, Pixels),
+  bytes_to_tuple(Mode, Bytes).
+
+luminance(<<R:8, G:8, B:8>>) ->
+  <<(trunc(R * 0.2126 + G * 0.7152 + B * 0.0722))>>.
+
+%% convert from rgb to grayscale
+convert(#bitmap{pixels=Pixels, mode=rgb}=Bitmap, gray) ->
+  Bitmap#bitmap{
+    pixels=array:map(fun(_I, Pixel) ->
+          luminance(Pixel) end, Pixels),
+    mode=gray};
+
+%% convert from grayscale to rgb
+convert(#bitmap{pixels=Pixels, mode=gray}=Bitmap, rgb)->
+  Bitmap#bitmap{
+    pixels=array:map(fun(_I, <<L:8>>) -> <<L:8, L:8, L:8>> end, Pixels),
+    mode=rgb};
+
+%% no conversion if the mode is the same with the bitmap.
+convert(#bitmap{mode=Mode}=Bitmap, Mode) ->
+  Bitmap.